Laser induced breakdown spectroscopy (LIBS) is a type of atomic emission spectroscopy which uses a highly energetic laser pulse as the excitation source. The laser pulse generates a high temperature micro plasma on the surface of the sample. After this excitation, light that is characteristic of the elemental composition of the sample is emitted and analyzed within a spectrometer. LIBS has become a very popular analytical method in view of some of its unique features such as applicability to any type of sample, practically no sample preparation, remote sensing capability, and speed of analysis.
A LIBS apparatus relies on the correlation between the concentration of elements and the intensity of their spectral lines to determine the composition of the target sample. Since most of the target samples are composed of many elements, which have closely spaced spectral lines in the wavelength domain, LIBS analysis requires a high wavelength precision for the spectrometer. Unfortunately, small wavelength drifts that are caused by environmental factors such as temperature and humidity variations or mechanical vibrations are unavoidable, especially for those portable LIBS apparatus which are used in field operations. These portable LIBS apparatus generally employ low resolution spectrometers without active temperature control. Yet even a tiny wavelength shift much smaller than the resolution of the spectrometer may cause large error in the predication of element concentration. Conventional solution to this issue is to utilize a standard light source (such as a mercury lamp) to perform frequent wavelength calibration. Such approach is both costly and time consuming. There thus exists a need for a LIBS apparatus which can perform wavelength calibration in a faster and more convenient way.